What does the System Average Interruption Frequency Index (SAIFI) represent?

The System Average Interruption Frequency Index (SAIFI) quantifies the average number of outages that customers experience over a defined period, typically a year. This index is calculated by taking the total number of customer interruptions and dividing it by the total number of customers served. It provides a clear measure of the reliability of the electricity supply from the customers’ perspective, as it focuses on how frequently they encounter service interruptions.

The other options do not accurately reflect the definition or purpose of SAIFI. Average energy consumption by customers relates to their usage patterns rather than interruption frequencies. Average restoration time for outages would align more with metrics such as the System Average Restoration Index (SARFI). Lastly, the duration of service interruptions describes how long outages last, which is measured by another index known as the System Average Interruption Duration Index (SAIDI). Thus, option B is the correct representation of what SAIFI indicates.